Process of treating paper pulp stock to insure uniform consistency



v G. P. BERKE'Y PROCESS OF TEEATING PAPER PULP STOCK TO INS URE UNIFORM CONSI STENCY Filed May 8. 1922 s E w w W W Patented Oct. 30, 1923.

GEORGE PHELPS IBIERIKEY, OF WISCONSIN RAPIDS, WISCONSIN.

PROCESS OF TREATING PAPER PULP STOCK TO IN SURE UNIFORM CONSISTEHCY.

Application filed May 8, 1922. Serial No. 559,294.

I To all whom it may concern: the invention consists in the process and the 55 I Be it known that I, GEORGE P. BERKEY, steps of the process hereinafter described a citizen of the United States, and resident and all equivalents. of Wisconsin Rapids, in the county of Ground wood or sulphite pulp stock com- Wood and State of Wisconsin, have invented ing from the grinders or digesters must new and useful Improvements in Processes be highly diluted, approximately 300 parts 60 of 'Treatin Paper Pulp Stock to Insure of water to one of stock in order to he niform onsi'stency, of which the followefi'ectively screened. The drawing shows ing is a description, reference being had a conduit 1 conducting the thin stock from to the accompanying drawings, which are the grinders or digesters to branch pi es apart of this specification. 2 leading to deckers or thickeners 3 which 65 he invention relates to paper-making remove the large amount of water used for and more particularly to a process for treat-- screening so as to make the pulp of thicker ing the paper pulp stock to insure a uniform consistency so that it is suitable for use consistency thereof when-the same is sent to in subsequent pulp or paper-mill apparatus,

the various machines and apparatus which or for the purpose of storage. These d eker to form it into paper. or thickeners 3 take this thin stock from With the so-called continuous process of the R P? 1 d d charge it as slush pulp ri l h k f th paper-making contalnlug parts of water to one of 20 machines in which the ground wood stock or stocksulphite pulp stock goin f i d Where the continuous process 18 used this digesters is passed through deckers or Slush P p 1S dISChEEPgBd I 3 l g Storage thickeners and then to a large storage tank tank 4 from a P P 5 Connect 9- t e from which the stock is drawn to mixing deckel's y j h plpes 6 and havlng a apparatus d fi ll t th paper a hi control valve 1 located in the line. When it was found that owing to the settling the la1'ge storage tank or tanks fl are filled action of the pulp in the large storage tanks h i p y 30 great that 2 1 th t; a r g lat was necessary f k i tlon W1th add1t1onal stock which is conthe consistency of the stock within certain stantly g p p d 11 may ake Several 30 limits after it was withdrawn from the tank. g y to mpty t em. What 1s usually done Su h g l t are known i th t as Is to use the storage tank or tanks for storage consistency regulators and can tak 3% of the Sunday productlon of pulp, on which stock or thicker and thin it down very day the other departments of the mill are satisfactorily and uniformly by adding closed down. During the Week h P p IS 35 water b t a large t f th t k i th gradually drawn out of the storage tank or storage tank is very thin stock, too thin tanks 4 for use 1n the mlll at the same time for use even though all of the water at the that ther pulp 1s belng made and supplied to consistency regulator be shut off, but the the ank but aS the rate of use of pulp consistency regulator annot thicke st k from the tank durlngtheweek is generally which is too thin and-as such stock is ingreater than is supplied during the weekvariably present in the so-called continuous days the tank Wlll emptied and again process where the pulp is drawn from a r ady f fu l harging at he end of he large storage tank, the present methods do Week. Holding slush pulp stock in storage not insure pulp stock of uniform consistency for even a few hours means that'a settling when the same is drawn from stock chests c ion takes place and that the consistency or tanks containing stock of varying c0ns ist- 0f the stock in storage will vary at difl'erent ency, Th obj t f thi i v t n is a depths throughout the tank. or lnstance, process for insuring not only the pmper such stock may vary from thick 4% stock functioning of the consistency regulator, t the bottom of the tank to Water at the but also to obviate the use of consistency top. Consequently, as the stock 1s drawn regulators where it is not necessary to mainoff from the storage tank for use it will vary 1 tain the consistency of the pulp within narwidely in consistency'and such variation is r li its, the cause or source of trouble and expense With the above and other objects in view in those processes to which the pulp is later great subjected which require pulp stock of uniform consistency for finished economical production.

To acquire uniform consistency and prevent settling various forms of mechanical agitators have been tried in the storage tanks, but the size of these tanks is so proved impractical and excessive in cost. The most widely adopted method in attempting to obtain uniform consistency is the use of various types of consistency regulators, the constructional features of which are well known to those skilled in this art. Such regulators all operate on the principle of adjusting the apparatus for a certain consistency of stock, and as the stock from the storage tank becomes thinner or thicker a device is actuated which shuts off or turns on a flow of Water into the stock. Such regulators obviously depend upon a supply of stock which is thicker than is wanted for use in the subsequent handling of the stock. Pulp stock is usually used at the consistency of 2% or'3% and consistency regulators can take 3% or thicker and thin it down very satisfactorily and uniformly by addingl water, but a large part of the stock in t e storage tank is very thin, too thin for use even though all the thinning water at the consistency regulator be shut off, so that the consistency regulator has not been found satisfactory because it cannot thicken stock which is too thin.

In order to insure stock of uniform thickness or consistency either with or without a consistenc regulator, where such stock is obtained rom large storage tanks in which, due to settling, it is of varying consistency, I provide for redeckering the stock taken from the storage tank since such redeckered stock will be of substantially uniform consistency as it leaves the deckers. This redeckerin may be done in separate deckers, but con itions of mill operations are such that the number of deckers or thickeners used in filling the storage tank or tanks 4 is generally greater than the number used when the stock is being drawn from storage. The result is that sufiicient deckers or thickeners are standing idle when stock is being drawn from storage so that the redeckering mentioned above may be carried out in the idle deckers. As in icated in the drawing, the slush pulp from the tank 4 is conducted through a pipe 8 to the deckers 3 in any suitable manner, as by means of a pump 9, and a control valve 10 is provided in the pipe 8 whereby the pulp from the large storage tank is pumped back over the deckers or thickeners and redeckered or thickened prior to its passage to the other machines which make it into the finished product. As is usual with the deckers, provision is made for adding water before redeckering so that that such mechanical agitators have the thick stock will work to better advantage in the deckers, but this water supply does not have to be regulated as the greater dilution of the thicker stock will not influence the uniform discharge of thick stock from the deckers so that the stock will be of uniform consistency regardless of a wide variation in the consistency of the stock g0- ing to the deckers and consequently the uniform consistency of the stock passing from the deckers after redeckering is assured and such stock as used in many products of the mill may be subjected to subsequent operations without the use of a consistency regulator.

In order that the How of the redeckered' slush pulp may be uniform, I provide a small tank 11 into which the redcckercd pulp may be discharged from the-de'ekers 3 through a branch 12 of the ipc 5, a centre valve '13 being located in tiis branch pipe. The stock is drawn oft from the small tank ll by a pump 14: through a pipe 15 at such a rate as to prevent a settling of the stock, in other words this tank 11 is provided to contain stock of uniform consistency. This condition is accomplished by making the smaller tank of such a size as to properly handle the volume of stock which will be pumped through it without giving the stock time to settle. As shown in the drawing, this tank may be formed in the main tank by providing a partition 16 adjacent-the main tank with the top 17 of its wall located slightly above the level of the pulp stored in the tank 4 so that it. may overflow into the larger tank. Since the consistency of the pulp in the small tank 11 can always be maintained within certain limits, the pulp from such tank may be pumped through the pipe 15 directly to other apparatus, such as continuous mixing system apparatus 18, from which the pulp is taken to various other machines or apparatus where it goes to make up the finished product. Vhere, however, it is desired to maintain the consistency of the slush pulp within relatively narrow limits a consistency regulator 19 of any suitable type is located in the pipe line 15, a pipe 20 being used to supply the thinning water to the consistency regulator, the general operation of which has been previously explained. Since the auxiliary tank 11 prevents pulp being delivered to the consistency re ulator of a consistency which is too thin or said regulator to handle, it is obvious that the consistency regulator when used with the redeckering, as above described, will properly perform its function of adding water to the stock coming into it if it is necessary, that is, if the stock is too thick, but it does not have to deal with the stock which is, too thin because of the relatively uniform consistenc of the stock introduced into the tank 11 from the deckers, which slush i which 1t has consistency is preserved because the stock does not have a chance to settle while in the tank 11. This tank 11 is placed in the sys-" f tem so as to insure enough slush pulp of the proper consistency being available when it is needed for immediate use in the mill.

What I claim as my invention is:

1. The method of withdrawing in a substantially uniform consistency thedec'kered 7 pulp from large storage tanks in which consistency, which consists in drawing the variable pulp from the tank as needed, adding water thereto and redeckering to a uniform consistency.

2. The method of withdrawing in a substantially uniform consistency the deckered slush pulp from large storage tanks, in settled so as to be of varying consistency, which consists in drawing the it has settled so as to be of'varying' yariable pulp from the tank as needed; addmg water thereto, and redeckering to a uniorm consistency and a thickness suitable for a. consistency regulator.

3. In paper-making where a plurality of deckers are used to furnish slush pulp to storage tanks for subsequent use, the method of withdrawing in a' substantially uniform consistency the deckered slush pulp from the storage tanks in which it has settled so GEORGE PHELPS BERKEY.

sists in drawing such pulp from store e as as to be of varying consistency, which con- 

